Process for the production of high molecular weight linear polyesters

ABSTRACT

A process for the production of high molecular linear polyesters by polycondensing a glycol with terephthalic acid or a terephthalic acid ester in the presence of a polycondensation catalyst. The condensation catalyst is a titanium-dioxide containing 0.01 to 20% by weight of a metal compound, preferably germanium dioxide and antimonium oxide is used as a metal compound. The catalyst can be prepared by calcinating titanium dioxide together with the metal compound.

United States Patent 151 3,674,747 Schnegg et a1. July 4, 1972 [54] PROCESS FOR THE PRODUCTION OF [56] References Cited gg g ggg'gg WEIGHT LINEAR UNITED STATES PATENTS 2,906,737 9/1959 York ..260/75 [72] Inventors: Robert Schnegg; Herbert Pelousek, both of 2,992,206 7/1961 Youle et al Dormagen; Robert Dippolhofer, Lever- 3,055,370 9/1962 n y kusen; Wolfgang Wiegrefie, Krefeld; l-lans- 3,057,908 1962 Gfuschke 8t Georg Voelz, Krefeld; Gerhard Kiengst, 3,074,913 1/1963 Davies et al. Krefeld, all of Germany 3,404,121 1/1968 Barkey ..260/75 [73] Assignee: Farbeniabriken Bayer Aktiengesellschaft, FORElGN PATENTS OR APPLICATIONS Leverkusen' Germany 740,381 11/1955 Great Britain ..260/75 [22] Filed: Dec. 17, 1969 I Primary Examiner-Melvin Goldstein [2]] Appl' 885973 AttorneyPlumley&Tyner [30] Foreign Application Priority Data ABSTRACT Jan. 17, 1969 Germany ..P 19 02 175.1 A process for the Production of high molecular "near polyesters by polycondensing a glycol with terephthalic acid 52 us. Cl. ..260/75 R, 252/437, 252/440, or tcrephthalic acid ester in the presence of a polycondensa- 252/461, 252/463, 252/471, 252/472 tion catalyst. The condensation catalyst is a titanium-dioxide 51 1m. (:1 ..C08g 17/015 Containing to 20% y Weight of a metal Compound, 58 Field of Search ..260/75, 75 c, 40 P Preferably germanium dioxide and ammonium Oxide is used as a metal compound. The catalyst can be prepared by calcinating titanium dioxide together with the metal compound 6 Claims, No Drawings PROCESS FOR THE PRODUCTION OF HIGH MOLECULAR WEIGHT LINEAR POLYESTERS This invention relates to a process for the production of linear high molecular weight polyesters containing a white pigment by polycondensing glycol terephthalates with catalysts incorporated on the titanium dioxide pigments used for the pigmentation.

Hitherto, glycol terephthalates have been polycondensed by the following method for example, terephthalic acid dimethyl ester and ethylene glycol are transferred in the presence of transesterification catalysts and polycondensed in vacuo following the addition of polycondensation catalysts and matting agents, thepigment and the catalyst being added either separately or mixed with one another before the polycondensation reaction.

It is an object of the invention to produce highly viscous, matted polyglycol terephthalates by using, as the polycondensation catalyst, a titanium dioxide in the anatase or rutile modification containing from 0.01 to 20% by weight of another metal compound acting as catalyst either incorporated in it or precipitated on to it. Oxides, phosphates or sulphates of the elements zinc, cadmium, antimony, copper, manganese, aluminum, magnesium, germanium, lead and cobalt, are used as the metal compounds. lt is preferred to use metal oxides in quantities of from 0.1 to 5% by weight. The metal oxides are either added to the titanium dioxide aqueous suspension before calcination or are introduced into the titanium dioxide after it has been calcinated in an after-treatment. In the first method, the metal oxide is incorporated in the titanium dioxide whilst in the second method the metal oxide is precipitated on to the titanium dioxide. The titanium dioxide provided with a metal oxide is added after transesterification in the form of a suspension in glycol or in an inert carrier. The concentration of titanium dioxide in the suspension amounts to between 0.5 and 70% by weight. Coated or calcined metal oxides are used in a quantity sufficient for the polycondensation reaction, i.e. in a quantity of from 0.005 to 0.5% by weight (of metal oxide) based on dimethyl terephthalate or terephthalic acid.

The process is suitable for the continuous production and batch production of polyesters and in particular for the production of polyglycol I terephthalates from dimethyl terephthalate and terephthalic acid with ethylene glycol or cyclohexane dimethanol. An appreciable technological advance is embodied in the fact that a synergistic effect is obtained, this being reflected in the fact that the polycondensation times are considerably reduced or higher melt viscosities and hence higher molecular weights are obtained for the same polycondensation times than those obtained in cases where the individual components are used as polycondensation catalysts.

The following Examples illustrate more particularly the invention:

I. Preparation of the catalysts used in accordance with the invention.

a. 0.40 of P (based on TiO in the form of l-l PO was was added with continuous stirring to a titanium hydrolysate slurry precipitated and washed in a known manner for the production of titanium dioxide by the sulphate process. After stirring for 1 hour, the sludge was filtered up to a solids content of 38.0%. 0.26% of K 0 (based on Ti0 in the form of a KOH solution and 5% of GeO (based on TiO in the form of an aqueous suspension of the oxide powder were then added and thoroughly kneaded with the paste. The paste was then dried and had a solids content of 70%. After drying, the product was sized-reduced in a mortar and then calcined in a rotary tube for 1.5 hours at 890 C. The calcine had an apparent density of 700 g/l. It was finely ground in a rotating ball mill. The germanium is either completely or partly incorporated into the crystal lattice of the titanium dioxide by this process.

b. An unutuse pigment prepared in a known manner by the sulphate process and ground up was mixed with water to form a 25% suspension and the resulting suspension was heated to 60 C. 0.9% of SiO, (based on TiO in the form of a waterglass solution containing 59.2 g of SiO /liter were then added with continuous stirring over a period of 15 minutes, followed by another 15 minutes stirring. 1.5% of M 0 (based on TiO )in the form of an aqueous Al,(SO solution containing g of A1 0 per liter were then added over a period of 15 minutes, followed by another 60 minutes stirring. The pH value was then adjusted to 5.0 by the addition of a 20% aqueous NH, solution, followed by another 30 minutes stirring. 1.05% of P 0,, (based on TiO in the form of an aqueous Na i-1P0 solution containing 42.5 g/liter were then added over a period of 10 minutes followed, after another 15 minutes stirring, by the addition of 0.3% of zinc (based on TiO in the form of an aqueous 10% ZnSO) solution. Stirring was continued for another minutes and finally the pH value was adjusted to 7.1 with the NH, solution (see above) in order to completely to precipitate the zinc phosphate (catalyst). The product was then filtered using suction and the filter cake washed with 10 times its quantity by weight of water at 80 C. The filter cake was dried for 15 hours at C and ground in a mortar. c. A rutile pigment prepared in known manner by the sulphate process and ground up was mixed with water to form a 25% suspension and the resulting suspension was heated to 60 C. 0.5% of 'l'iO- (based on TiO pigment) in the form of a titanyl sulphate solution containing 120 g of TiO, per liter were then added with continuous stirring over a period of 15 minutes, followed by another 60 minutes stirring. 2.8% of NaOH (based on TiO in the form of a 50% sodium hydroxide solution were then added over a period of 15 minutes followed by 60 minutes stirring. 1.0% of A1 0 (catalysts [based on TiO pigment in the form of an Al 50,), solution containing 100 g of A1 0 per liter were then added over a period of 15 minutes, followed by 60 minutes stirring. The pH value was then adjusted to 7.07.2 with more Al (SO solution. (pH- values below 7.0 are corrected to 7.0-7.2 by the addition of 50% sodium hydroxide solution). To adjust to the correct pH- value stirring was continued for minutes. The product was then filtered using suction and the filter cake washed with 10 times its quantity by weight of water at 80 C. The filter cake was dried at 150 C for 15 hours and ground in a mortar. d. 1% of SiO (based on TiO in the form of a waterglass solution containing 59.2 g of Si0 per liter was added with continuous stirring over a period of 15 minutes to a 25% rutile pigment suspension prepared in accordance with Example 3 after it had been heated to 60' C, followed by another 15 minutes stirring. On completion of the addition, the product has a pH-value of 11.6. 0.4% of Sb (based on TiO in the form of an SbCl solution containing 299 g of SbCl per liter were then added over a period of 10 minutes, followed by another 15 minutes stirring. In order to completely precipitate the Sb (V) oxide hydrate, 25% sodium hydroxide solution is then added until the pH value is 8.5. After 30 minutes stirring, the product is filtered by suction, washed, dried and ground as in C). II. Preparation of the linear high molecular weight polyesters according to the invention EXAMPLE 1 80 kg of terephthalic acid dimethyl ester and 70 kg of ethylene glycol were transesterified for 3 hours at 180 C with 60 g of calcium acetate (0.075%) based on dimethyl terephthalate, 71 l g of a 48% suspension of anatase with GeO according to a) in glycol (approximately 0.426% of TiO based on DMT) being added before precondensation. The concentration of germanium dioxide in the pigment amounts to about 4.5% by weight, based on TiO After a gradual increase in temperature to 285 C followed by evacuation to 0.] Torr, the reaction mixture was polycondensed for 2.5 hours at upwards of 1 Torr. A highly viscous matted polyester with the following characteristics is obtained:

'nrel' m.p.

remission (at 460 m 73% 280 3100 poises *1 was measured with a 1% by weight solution in m-cresol at 20C. COMPARISON EXAMPLES m.p. 256C remission (at 460 mp.) 68% 1 280 1560 poises 1 was measured with a 1% by weight solution in m-cresol at 20C.

It can be seen that a polyester of greatly increased viscosity and better whiteness is obtained according to Example 1 under the same conditions. b. 80 kg of terephthalic acid dimethyl ester and 70 kg of ethylene glycol were transesterified for 3 hours at 180 C with 60 g of calcium acetate (0.075% based on DMT), 15.2 g (0.019% by weight) of GeO and 0.426% by weight of TiO being added before precondensation. A gradual increase in temperature to 285 C and evacuation to 0.1 Torr are followed by 2.5 hours polycondensation at upwards of 1 Torr. A highly viscous polyester with the following characteristics is obtained:

'qrel 1.56

m.pp 258C remission (at 460 my.) 72% n280 2050 poises These figures are proof of the synergistic effect of the multicomponent catalysts according to Example 1 used in accordance with the invention in comparison with an ordinary mixture of the catalyst components.

EXAMPLE 2 80 kg of terephthalic acid dimethyl ester and 70 kg of ethylene glycol are transesterified for 3 hours at 180 C with 60 g of calcium acetate (0.075% based on DMT), 711 g of a suspension (48% by weight) of anatase pigment similar to Example 2 coated with zinc phosphate (ZnO concentration in the pigment approximately 4.5% by weight based on TiO in ethylene glycol being added before precondensation. A gradual increase in temperature to 285 C and evacuation to 0.1 Torr were followed by 2.5 hours polycondensation at upwards of 1 Torr. A highly viscous matted polyester with a satisfactory grain size distribution is obtained:

nrel 1.58

m.p. 258C remission (460 my) 69% 1 280 2400 poises Remission degree was determined EXAMPLE 3 80 kg of terephthalic acid dimethyl ester and 70 kg of ethylene glycol were transesterified for 3 hours at 180 C with 60 g of calcium acetate (0.075% based on DMT), 71 1 g of a suspension (48% by weight) of rutile pigment coated with Sb (V) oxide hydrate (2% by weight of Sb O based on TiO- in ethylene glycol being added before precondensation. A gradual increase in temperature to 285 C and evacuation to 0.1 Torr were followed by 2.5 hours polycondensation at upwards of 1 Torr. A highly viscous matted polyester with a satisfactory grain size distribution is obtained:

nrcl 1.61

LII

m.p. I 261C remission (at 460 mp.) 68% 17280 2800 poises Remission degree was determined EXAMPLE 4 10 kg of terephthalic acid dimethyl ester and 8 kg of ethylene glycol/hour were continuously transesterified at C with a solution of 0.05% by weight of zinc acetate in a continuous transesterification cascade, and on completion of transesterification a 48% suspension (89 g/hour) of anatase with GeO (according to Example 1) in glycol (approximately 0.43% of TiO based on DMT) is continuously added through metering pumps so that a concentration of 0.019% by weight of GeO is adjusted in the melt (concentration of GeO in the anatase approximately 4.5% by weight). After continuous precondensation in a screw reactor, condensation is completed in a polycondensation screw (280 C; 0.1 Torr; residence time 1.5 hours).

'nrel l .64

m.p. 258C remission 72.0%

EXAMPLE 5 50 kg of terephthalic acid are esterified for 2 hours under pressure at 240 C in an autoclave with 40 kg of ethylene glycol and 25 g of zinc acetate, and the steam continuously injected at 5 atms. After reaching normal pressure, 445 g of a suspension (48%) of anatase with GeO according to Example 1 in glycol are added (approximately 0.43% of TiO based on TS). The concentration of GeO in the pigment amounts to 4.5% by weight. The temperature is increased in stages to 75 C whilst at the same time the autoclave is evacuated to a pressure of 1 Torr (2.5 hours at upwards of 1 Torr) nrel 1.71

m.p. 250C remission 69.0% EXAMPLE 6 2,5 kg (17,4 mol) of 1,4-cyc1ohexanedimethanol, 1,3 kg (6,7 mol) of dimethylterephthalate were transesterified for 3 hours at 200 C in the presence of 1,3 g (0.1% by weight calculated on dimethylterephthalate). The temperature is raised for 15 minutes to 220 C and l 1,08 g ofa suspension (50% by weight) of the catalyst prepared according la) are added. The titan content was approximately 0.426% by weight of titaniumdioxide based on dimethylterephthalate and the concentration of the germanium dioxide amounts to about 4.5% by weight based on TiO After a gradual increase of temperature to 300 C followed by evacuation to 0.2 Torr in 15 minutes, the polycondensation reaction was finished after 3 hours. A

highly viscous melted polyester is obtained.

nrel

m.p. 292 to 249C remission (at 460 my) 78% 1,300 3900 poises What we claim is:

1. In the process for the production of high molecular weight linear polyesters which comprises polycondensing a glycol with terephthalic acid or a terephthalic acid ester in the presence of a catalyst the improvement comprising using as said catalyst titanium dioxide with from 0.01 to 20% by weight based on the titanium dioxide of a metal compound comprising an oxide, phosphate or sulfate of the metal zinc, cadmium, antimony, manganese, aluminum magnesium, germanium, lead or cobalt; said catalyst being added in the form of a suspension in glycol or an inert carrier in which the suspension contains 0.5 to 70% by weight of titanium dioxide; said catalyst being prepared prior to use in polycondensation by A. calcining titanium dioxide together with said metal compound; or by B. heating an aqueous suspension of titanium dioxide with a solution of a water soluble salt of the metal of said metal compound. precipitating said metal compound onto the titanium dioxide, washing and drying the product.

2. The process as claimed in claim 1, wherein said metal compound is germanium dioxide.

3. The process as claimed in claim 1, wherein said metal compound is zinc phosphate.

a titanium dioxide calcined together with the metal compound.

6. The process of claim 1 in which the metal compound is an oxide and the metal compound is present in an amount of 0.] to 5% by weight based on the titanium dioxide.

0 I 1 i i 

2. The process as claimed in claim 1, wherein said metal compound is germanium dioxide.
 3. The process as claimed in claim 1, wherein said metal compound is zinc phosphate.
 4. The process as claimed in claim 1, wherein said metal compound is an antimony oxide.
 5. The process as claimed in claim 1, wherein said catalyst is a titanium dioxide calcined together with the metal compound.
 6. The process of claim 1 in which the metal compOund is an oxide and the metal compound is present in an amount of 0.1 to 5% by weight based on the titanium dioxide. 